In WO 96/39269, a method for the chip-removal machining of cylindrical correctors and a device for carrying out this method are described. The cited method uses a so-called cut division in which, in the production of the final contour which can be to the final dimensions or can still have a certain amount to be removed and which can be taken off by grinding or polishing, tools are used which are fitted with cutting inserts disposed one after another or which can simultaneously engage with the workpiece. In the case of a crankshaft, the cheeks are machined and undercuts are formed and the pins of the crankshaft or the formation of a half crankshaft cheek with an undercut or a diameter portion can be formed with a first tool and a second undercut and the remaining portion of the diameter with a second tool. The subdivision enables a variation of the bearing width within certain limits. Preferably the machining is carried out by so-called high-speed milling in which the tool is driven with a constant high speed or with a variable speed. In high-speed milling, a cutting speed of more than 160 m/min is used. The chip thickness is in the range of 0.05 to 0.1 mm. The length of the tool carrier over which the corresponding cutting insert is engaged relative to its total length is selected to be as small as possible. With this feature, surface quality can be achieved that is so high that the preliminary grinding or additional pretreatment required prior to the heat treatment as additional process steps can be completely eliminated. With the method described in WO 96/39269 it has been proposed to provide different tools with turning cutting plates for cheek machining on the one hand or for pin machining and for undercutting on the other. All of the cutting inserts used had positive rake angles whereby the cutting insert settings with respect to the workpiece were such that the effective rake angle varied between xe2x88x925xc2x0 and +15xc2x0, preferably xe2x88x925xc2x0 to +5xc2x0 and/or had a positive axial rake angle (back rake angle) up to 10xc2x0.
In a there-described special embodiment, a side-milling cutter had two types of cutting plates of which one type were radially clamped to the tool carrier and the second type were tangentially clamped to the tool carrier or tool receiver.
If the side-milling cutter has on its cylindrical peripheral surface two rows of tangentially clamped cutting plates disposed next to one another in the case of finishing inaccuracy or with a divided tool, a step can develop with position inaccuracies of the machine tool by means of which, in the overlap region of the machined workpiece an undesirable sharp-edged setback can arise. To prevent this over-cut, WO 96/39269 has proposed a cutting insert whose rake surfaces in the region of a cutting corner and the main cutting edge are beveled or set in a region extending over both neighboring main cutting edges. Such cutting inserts enable the formation of clean transitions in the overlap region, for example in the production of the pin surfaces of a crankshaft lifter pin.
In WO 96/39260, radially clamped cutting inserts have been illustrated for forming an undercut in a crankshaft.
In DE 197 39 300 A1, a cutting insert has been described for the cutting of structural shapes, especially for milling of profiled cuts in rotating workpieces like crankshafts. These cutting inserts have a substantially cubical base body with at least two useful cutting edges, two mutually parallel, planar side faces traversed by a fastening bore, two base surfaces which at their opposite ends each form a cutting edge which has an arc shape corresponding to the profile to be cut and is bounded by a rake surface. The free surface between two opposite cutting edges should be at least partly circularly concave. Because of the concave-free area configuration, there is a clearance angle enlargement and a greater clearance space open toward the middle of the clearance surface whereby a desired tilt of this cutting insert relative to the workpiece is enabled.
It is an object of the present invention to further develop a side-milling cutter of the type described at the outset so that softer cutting during machining is ensured.
With the side-milling cutter according to the invention the object of enabling the greatest possible number of cutting tools to be mounted on the provided cylindrical periphery of the side-milling cutter is attained in that the tangentially clamped cutting inserts are at an axial inclination angle of 25xc2x0xc2x110xc2x0, preferably at an inclination angle of 20xc2x0 to 30xc2x0. Seen opposite the mill rotation direction, the rearmost cutting corner of such a cutting insert lies at a straight line perpendicular to the direction of rotation of the side mill cutter which is spaced from the leading cutting edge of the subsequent radially clamped cutting insert by a distance ofxe2x89xa65 mm, preferablyxe2x89xa62 mm and extending into negative values.
With side-milling cutters known from the art, the setting of the axial angle is limited to small values in order to keep the spatial requirements of the tangentially clamped and preferably square rake surfaces on the cutting inserts on the periphery as small as possible since a tilting around an axial angle requires a respective spacing from the next following radially clamped cutting insert taking into consideration the enlarged rake chamber formed on the tool carrier. With the selected axial angle inclination for the tangential cutting insert of the invention, is however possible to swing the rearmost cutting corner to the cutting insert inwardly so that its spacing, measured by means of a straight line lying perpendicular to the milling direction, from the cutting edge of the next following radially clamped cutting insert can be reduced preferably from less than 2 mm to even negative values. By negative spacing values an arrangement is understood for the tangentially clamped cutting inserts in which the rearmost cutting edge is spatially located behind the cutting edge of the next following radial cutting insert. With the chosen arrangement it is possible to increase the number of useable cutting inserts on the tool carrier. Preferably the side-milling cutter has, as seen in the direction of cutting, an alternating sequence of tangentially and radially clamped cutting inserts on the cylindrical periphery of the tool carrier or, as stated otherwise, radially clamped cutting inserts along the edges of the side-milling cutter cylinder which respectively (left as well as right) is spatially disposed ahead of a respective tangentially clamped cutting insert. The two rows thus formed of tangentially clamped cutting inserts have cutting inserts which, depending upon the row with which they are associated, have a tilt about an axial angle in the opposite sense from another cutting insert of the other row.
For the machining of cylindrical surfaces without undercuts, a portion of the tangentially clamped cutting inserts can be omitted as will be apparent from the description of FIGS. 4 and 5. In this arrangement there is a spacing of the rearmost cutting corner of such cutting inserts as taken along a straight line which is perpendicular to the cutting direction of the side mill cutter, from the reading cutting edge of the next following radially clamped cutting insert of a distance ofxe2x89xa710 mm, preferablyxe2x89xa75 mm to negative values.
Preferably the tangentially clamped cutting inserts are so arranged that the shortest distance of the cutting edges which are inactive during machining or their extensions which are turned toward the edges of the side-milling cutter cylinder, to the next following cutting corner of the subsequently arranged radially clamped cutting insert in the cutting direction is selectedxe2x89xa71 mm. Through this feature it is ensured that a sufficient place for the requisite rake chamber remains ah ad of the radially clamped cutting insert and chip running off from it does not collide with the inactive cutting edge toward the rake chamber of the tangentially clamped cutting insert or can damage this cutting edge. This is especially of significance for so-called turning cutting plates which respectively have four useable cutting edges. A preferred measure for the axial inclination angle of the tangentially clamped cutting inserts is 25xc2x0.
According to a further feature of the invention, the cutting regions of two successive tangentially clamped cutting inserts overlap slightly.
With the side-milling cutter according to the invention, cutting speeds of 160 m/min and greater chip thicknesses of 0.1 mm to 0.25 mm can be removed.